Greste, producer Mohamed Fahmy and producer Baher Mohamed, were arrested December 29 at a Cairo hotel room and later charged with joining a terrorist organization -- the blacklisted Muslim Brotherhood, as well as broadcasting false information and working in Egypt without permits.

Reports said Mansour's letter was in response to one sent by the Al Jazeera English journalist's parents.

"As a father I'd love to convey my understanding of the prevailing emotions of distress and anguish amongst both Peter and the whole family," Mansour wrote in the letter, which was published by his office.

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"Notwithstanding the independence of the judiciary and that his full rights are guaranteed under the law, I would like to assure you in my capacity as President of Egypt, that I will spare no effort to work towards the speedy resolution of the case, in a fashion consistent with the law and that guarantees the reunion of the family in the near future."

International condemnation

Earlier this month, prosecutors presented evidence at a hearing for the three journalists, but they did little to explain why everyday broadcast equipment and the defendants' personal belongings would implicate them in any crime.

Throughout the hearing, the defendants were kept in a caged dock steps away from their family members.

The three are among 20 defendants authorities have charged with crimes; the Qatar-based Al Jazeera says only eight have worked for the network.

The trial has drawn international condemnation from human rights groups, who say the arrests indicate authorities in Egypt are stifling dissent and freedom of the press.

The case comes amid a crackdown on the Muslim Brotherhood after the ouster of Egypt's first democratically elected president, Mohamed Morsy, in July. The accused have denied the allegations against them, with the journalists saying they were simply doing their jobs.